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INVENTIONS OF NIKOLA TESLA.

cal connection through the arc formed. Now this arc is formedwhether there be resonance or not. Blit even if the spark wouldnot be produced, still there is an alternating e. m. f. set up betweenthe bodies when the plate is brought near one of them ; thereforethe approach of the plate, if it does not always actually, will, at anyrate, tend to break down the air space by inductive action. Insteadof the spheres or plates a and b we may take the coatings of a Ley-den jar with the same result, and in place of the machine,—whichis a high frequency alternator preferably, because it is more suit-able for the experiment and also for the argument,—we may takeanother Leyden jar or battery of jars. When such jars are dis-charging through a circuit of low resistance the same is traversedby currents of very high frequency. The plate may now be con-nected to one of the coatings of the second jar, and when it isbrought near to the first jar just previously charged to a highpotential from an influence machine, the result is the same as be-fore, and the first jar will discharge through a small air spaceupon the second being caused to discharge. But both jars andtheir circuits need not be tuned any closer than a basso profundois to the note produced by a mosquito, as small sparks will be pro-duced through the air space, or at least the latter will be consider-ably more strained owing to the setting up of an alternatinge. m. f. by induction, which takes place when one of the jars be-gins to discharge. Again another error of a similar nature is quiteeasily made. If the circuits of the two jars are run parallel andclose together, and the experiment has been performed of dis-charging one by the other, and now a coil of wire be added to oneof the circuits whereupon the experiment does not succeed, theconclusion that this is due to the fact that the circuits are nownot tuned, would be far from being safe. For the two circuitsact as condenser coatings and the addition of the coil to one ofthem is equivalent to bridging them, at the point where the coilis placed, by a small condenser, and the effect of the latter mightbe to prevent the spark from jumping through the discharge spaceby diminishing the alternating e. m. f. acting across the same.All these remarks, and many more which might be added but forfear of wandering too far from the subject, are made with thepardonable intention of cautioning the unsuspecting student, whomight gain an entirely unwarranted opinion of his skill at see-ing every experiment succeed; but they are in no way thrust uponthe experienced as novel observations.